animal instincts

When Dogs Are Driven

New insights into Fido’s compulsive streakby nicholas dodman

Some years ago, I was accosted by a breeder of bull terriers who asked
me to explain why one of his dogs constantly spun in tight circles, trying—it
appeared—to catch his own tail. A short while later, a woman asked me if
I could do something to prevent her Doberman pinscher from sucking its
flank. Then there was a Norfolk terrier who constantly snapped at nonexistent
flies.

What is it with dogs like these? I wondered. As it turns out, they have canine (obsessive-)compulsive disorder. “Obsessive” is in parentheses because you can’t prove that a dog obsesses, but there can be no arguing about the compulsive nature of the behaviors. They seem to stem from frustration, in that such dogs have little or no opportunity to follow the natural instincts of their breed. Put another way, they are all dressed up (for some serious biological purpose) with no place to go.

Our first real glimmer of understanding came from a child psychiatrist. In the early 1990s, Judith Rapoport published an article describing how human anti-obsessional drugs had been successfully used to treat dogs with “acral lick dermatitis,” a condition marked by repetitive licking of the lower extremities. This landmark paper provided a fresh perspective on problems that veterinarians in the trenches had long struggled with. A diagnosis of canine compulsive disorder (CCD) entered the realm of animal behavioral parlance, and new therapies ensued.

At first, my research collaborator—Louis Shuster, professor emeritus of pharmacology, biochemistry, and neuroscience at Tufts Medical School—and I were confused. We had discovered earlier that some repetitive disorders in various species could be treated with chemicals that block opioids (compounds created naturally in the body that resemble opiates). From this we deduced that the animals grew addicted to certain feel-good chemicals—such as endorphins, a type of opioid—that their bodies produced when they engaged in the compulsive behavior. We had a hard time reconciling Rapoport’s findings with our own, but then the penny dropped. We realized that opioid blockers also block glutamate, a neurotransmitter that plays a role in compulsive behaviors. Our opioid blockers and Rapoport’s anti-obsessional drugs both worked by making the nerve terminals release less glutamate.

Since then, we have observed that spinning bull terriers respond both to opioid blockers and to anti-obsessional drugs. So do flank-sucking Dobermans and madly fly-snapping Norfolk terriers. We have gone on to treat dogs that chase lights or shadows, dogs that run in geometric patterns, dogs that compulsively eat inedible objects, and dogs that are forever barking up the wrong tree.

Now we are searching for the gene or genes responsible for these bizarre afflictions. If we succeed, we could shed light on the genetic factors underlying obsessive-compulsive disorder in humans. After all, from a biological perspective, canine and human compulsive behaviors are remarkably alike. Both are linked to anxiety and involve similar parts of the brain. Both respond to the same medications.

Perhaps most significant, both call to mind the sorts of tasks that, in another context, might ensure survival. They tend to concern hunting, or gathering, or grooming, or personal safety—all of which suggests that they’re hard-wired. We need to remember that compulsions are not all bad. Dogs that will not stop chasing squirrels may get more to eat than their more laid-back peers. People who fret about safety might live longer and have a better chance to spread their genes. A professor who will not give up on an idea might be more likely to produce a sound theory and achieve academic success. It’s only when a person or dog obsesses (there, I said it) to the point of dysfunction that a problem arises. And thereby, as we say in the dog behavior business, hangs a tail.

NICHOLAS DODMAN directs the Animal Behavior Program
at the Cummings School of Veterinary Medicine and has written four bestsellers
in the field. He is the editor of Puppy’s
First Steps: The Whole Dog Approach to Raising a Happy, Healthy, Well-Behaved
Puppy (Houghton-Mifflin, 2007) and a pet expert
for Time Inc. and Life magazine.